In carburetors for small internal combustion engines of the type used on power saws, lawn mowers and the like, various devices have been used to limit the rotation of the fuel regulating valves to limit the extent to which the amount of fuel supplied to the engine can be increased after the regulating valve has been adjusted during manufacture of the internal combustion engine.
One device limiting adjustment of a carburetor fuel regulating valve is disclosed in Japanese patent laid-open application Publication No. 6-102093. This laid-open application discloses a lid mounted on a head of the fuel regulating valve in order to obstruct the rotation of the fuel regulating valve in the direction of increasing fuel. When the lid is mounted on the head of the fuel regulating valve, a coil spring is utilized for suppressing movement of the fuel regulating valve. However, the rotational position of the fuel regulating valve sometimes deviates from its adjusted position. That is, there is a problem in that after completion of the adjusting operation of the fuel regulating valve, the fuel regulating valve is sometimes moved back by the force of the coil spring so that the amount of fuel delivered is changed. Further, since the head of the fuel regulating valve projects from the carburetor body, if an operator breaks the lid intentionally, the fuel regulating valve can be adjusted in the direction of increasing the amount of fuel.